Secure Maximum Value Computation With Parallel Encrypted Comparisons
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Solution Overview
Problem
The existing methods for computing the maximum value and flag of encrypted numerical values require a large number of comparison stages, resulting in inefficient processing time proportional to Θ(n).
Innovation Solution
A secure maximum value computation apparatus and method that reduces processing time by performing comparisons in a single stage or fewer stages using a set of secret values, employing an output unit, comparison unit, flag computation unit, and maximum value computation unit to determine the maximum value and its corresponding flag efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sequential comparison method is used to compute maximum value of n encrypted values, then the computation can be performed securely without restoring encrypted numerical values, but the number of comparison stages and total comparisons becomes as large as Θ(n), resulting in inefficient processing time
Solution Approach 1:
The patent divides the set of n encrypted values into multiple subsets and performs parallel comparisons within each subset. By segmenting the comparison task across multiple groups that can be processed simultaneously, the number of sequential comparison stages is reduced from Θ(n) to a constant number of stages, thereby improving processing time while maintaining secure computation through encrypted value comparisons.
2Productivity
If parallel comparison method is used to reduce comparison stages, then processing time is reduced, but the complexity of coordinating multiple comparison operations increases
Solution Approach 1:
The patent combines multiple comparison results from different subsets using logical operations on encrypted values. By merging the results through encrypted logical AND operations and subsequent encrypted maximum value computations, the system coordinates parallel comparisons without increasing the cryptographic complexity, as all operations remain within the encrypted domain using standard secure computation primitives.
Data Source
AI summary
A secure maximum value computation apparatus, assuming that a set X={[[x1]], [[x2]], . . . , [[xn]]}, includes an output unit 1 that outputs [[x1]] and [[1]] as a maximum secret value [[y]] and a flag [[z(x1)]], respectively, when n=1 holds, a comparison unit 2 that computes a comparison result of which is larger with respect to a predetermined order for each pair {[[xi]], [[xj]]}⊂X of elements of the X, a flag computation unit 3 that computes whether all comparison results related to each of the [[xi]]s are “large” for each of the [[xi]]s to set a computed value as a flag [[z(xi)]], and a maximum value computation unit 4 that uses the [[z(xi)]] to computes a maximum value [[y]].